Technical Field
The present invention relates to an electronic component built-in substrate and an electronic component device.
Related Art
In the related art, there are electronic component built-in substrates such as semiconductor chips and capacitors. In such electronic component built-in substrates, electronic components are disposed in cavities formed in core substrates, and wiring layers are connected to those electronic components.    [Patent Document 1] Japanese Patent Application Publication No. 2007-103939A    [Patent Document 2] Japanese Patent Application Publication No. 2011-142286A
As will be described below with a preliminary technology, in some electronic component built-in substrates, cavities are formed in core substrates at predetermined depths in the thickness directions, and capacitors are mounted on the bottom plate portions of the cavities. Further, the upper surfaces and side surfaces of the capacitors are sealed by first insulating layers, and on the lower surfaces of the core substrates, second insulating layers are formed.
In such an electronic component built-in substrate, the structure of an area around a capacitor in the thickness direction is asymmetric with respect to the capacitor. Therefore, during a heating process, if thermal stress is generated due to a difference in the coefficient of thermal expansion between elements, the substrate is likely to be warped.
Also, since the bottom of the cavity of the core substrate has no opening, the core substrate is susceptible to contraction stress which is generated when a first insulating layer is formed to seal the capacitor, and thus the core substrate is likely to be warped.